DE2223044A1 - Control circuit for direct current electric motors - Google Patents

Description

PATENT LAWYERS Dipi.-ing. H. Seiler Dipi.-ing. J. Pfenning Dipi.-Phys. KH Meinig

1 Berlin 19

Oldenburgallee 10 Tel. 0311/304 55 21 80 563 304 55 22

Wireword: Seilwehr patent j Postscheckkto. Bln.W. 59 38

May 8, 1972 Me / St

CABLEFORM LIMITED

Green Lane, Romiley nr. Stockport

Cheshire, England

Control circuit for direct current electric motors

The invention relates to control circuits for controllable direct current electric motors, for example for a means battery-operated motor as it is used in vehicles that have run down batteries.

Such control circuits carry the current of a direct current source, namely a battery, the motor via a thyristor circuit, pulse-controlled, whereby the condition The pulses from a pulse generator is given by changing the energy supply to the motor via the change in frequency and / or the pulse-spacing ratio of the generator pulses can be kept variable.

209848/0832

With such an arrangement, the electrical braking by actuating a reversing switch, which reverses the field direction in the motor, or winding connections reversed polarity. Due to the high emf generated and the corresponding currents, however, the field current is particularly intense Braking relatively low.

The invention is therefore based on the object of developing a control circuit for the stated purpose, by means of which it becomes possible to supply high field currents to the motor after and before the reversing switch has been operated the engine has come to a standstill.

The solution to this problem is to create a control circuit for controlling a direct current electric motor with an armature and a field and a diode connected to the armature winding, which is then biased accordingly reversed polarity when the motor is in its driving state, with a DC switch supplies current pulses to the motor and aids are provided that determine whether and when the armature current exceeds the field current during one or each current pulse, and finally means for limiting a Current range that can be applied to the motor when the armature current exceeds the field current above a predetermined Value, are present.

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According to the invention, a control circuit for controlling a DC electric motor with an armature and a field created, with a diode connected in parallel with the armature which is biased with reverse polarity when the motor is operated. A DC switch belongs to the control circuit, which supplies current pulses from a direct current source for the motor and which changes the pulses with respect to their frequency and / or their spacing ratio in accordance with a control signal, the circuit also includes a capacitor, which with the beginning of each Current pulse begins to charge and can be discharged via switching means, which are then in their conductive State when the said, parallel to the armature diode is biased or biased in the opposite direction is. Furthermore, means are provided which determine during each pulse whether the capacitor is a has reached a certain predetermined level of charge with a full range of currents being applied to the engine can, if the predetermined amount is not reached, and only then a limited range or better a corresponding one Current interval can be applied when the specified value is reached.

With the arrangement of the armature diode, the current in the armature is always equal to or greater than that in the field winding, if the DC switch is on.

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When the armature is stationary or a back emf to the battery voltage is supplied, the diode is reverse biased, and armature and field currents are the same. When the anchor is down against is in its energizing state, an excitation current is passed through the diode which is above that of the Field, i.e. it is then biased in the forward direction. In this respect, the diode can be forward-biased be during an interpulse period when the anchor time constant is greater than that of the field.

The arrangement according to the invention distinguishes between a motor and a generator-like state, without a Confusion due to the forward bias during the interpulse period would be possible.

In the motorized state, a current that is still present in the armature is very small at the end of an intermediate pulse period. if the DC switch is on, the field current increases and reaches the within a very short time Value of the armature current, at which point the voltage is reversed on the armature diode.

On the other hand, if the engine works like a generator, it becomes;

Current of the armature diode over the entire pulse ^ intermediate period j

held at a high value while the field current drops as before. After switching on the DC switch,

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the electricity takes a much longer time to reach it the current value of the armature, so that strong braking can never be achieved under these conditions.

This makes it possible to clearly distinguish between the motor-driven and the generator-like or generating state according to the measurement the time delay (j) between switching on, the DC switch and the inverse of the armature diode bias.

An embodiment of the circuit according to the invention is described below with reference to the accompanying drawings. It means:

Fig. 1 is a schematic circuit diagram of an inventive Control circuit and

Fig. 2 Diagrams of voltage and current in different Sections of the circuit according to Fig * I.

As can be seen from Fig. 1, a DC switch S, the field F and a fitting or a are in the control circuit Armature A of an electric motor in series, over which a battery voltage drops, which with its poles the voltage values + Vb and -Vb. A diode Dl is parallel to the armature A

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switched so that they are biased in the reverse or blocking direction during normal motorized actuation of the armature is. Another diode D2 is parallel to the field F, i.e. a winding that defines it and the one with it in series armature A. The DC switch S carries current pulses with a variable frequency and / or variable Pulse spacing of the field-anchor arrangement, whereby the average power supply for the motor can be varied. The DC switch essentially consists of a thyristor circuit with known collecting means, the conductive state of the thyristors is determined by a gate pulse signal controlled by pulses emitted by a pulse generator, not shown, which form the base of the transistor T3 are fed, the collector of which via a resistor Rl to the direct current switch S and further is connected to a capacitor Cl via a diode D3 and the charge resistor R2.

At the beginning of each gate pulse, the capacitor C1 begins to be charged and the switch S supplies power to the motor. if any current in the armature causes the field current to increase until it reaches the armature current, the polarity of the diode Dl is reversed or biased in the opposite direction and the transistor Tl, whose base-emitter circuit is parallel to the armature is switched to the conductive state, so that the transistor T2 is also conductive and the capacitor Cl

discharges. . -7-

2098 4 8/0832

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In the start-up or generally in the motor state of the motor, the field current of the same increases and reaches in a very short time the armature current, whereby only a very low charge of the capacitor C1 can be achieved. When the engine on the other hand, should work as a generator, or when it is in its generating state, i.e. when it is for Execution of a braking process is used, then the armature current is extremely large and the field current is required a very long time interval to reach the value of the armature current, so that the capacitor C1 is continuously charged can until it has reached the voltage limited by a Zenner diode ZDl. Under these conditions then the Zenner diode ZDl conductive, and a signal fed to a pulse generator (not shown) leads to the restriction the current range or interval that can be fed to the motor, for example to limit the maximum Pulse frequency, the current that is present in the motor during conditions that are characterized by the braking process are, can be supplied.

2 shows current diagrams for different sections of the control circuit. The pulse shapes (a) and (g) show the gate pulse signals transmitted to the thyristor circuit in be fed to the DC switch. The pulse waveforms correspond to the signals at the base of the transistor T3

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from the pulse generator. The same signals are applied to the charging circuit through the diode D3, the resistor R2 and the Capacitor Cl is given.

The pulse diagram (b) corresponds to the voltage drop across the diode D2 and thus the voltage drop across the series connection from field F and anchor A.

The waveform (c) represents the voltage curve that drops across the armature diode Dl when the armature is in its motorized position State is, the solid line shows the voltage when the armature current Ia corresponds to the curve IaI follows the waveform (d), while the broken line shows the difference when the armature current corresponds to curve Ia2 follows.

The wave form (d) shows the current curves for the field current I: and the two aforementioned amounts of IaI and Ia2 of the armature current for the motor condition.

The wave form (e) shows the current curves for the field current If and the two values of the armature current Ia3 and Ia4, when the motor works as a kind of generator during the braking process.

209848/0832

The wave form (f) shows the voltage ₉ which drops across the armature diode Dl when the motor is in the generator-like state, the broken line indicating the difference when the armature bga _o follows the armature current Xa4 ₉ during the fully marked Line refers to the armature current Ia3. The time delay ff between the start of the gate pulse and the reversal of the voltage ₉ which drops across the diode is readily apparent

When setting a permissible time delay ₉ d "ho when setting the resistance value R2 and / or a corresponding value for the capacitor C1, it is possible to specify a threshold value speed for the electrical braking, as well as for the start and reversal of the increase in inclination.

The advantages of the described and illustrated in the drawings Arrangements according to the invention are essentially the following:

a) The operator of the vehicle can start it with a high repetition rate and apply it for braking reset to a low rate. This avoids any delays in the normal starting process, as is usually the case with facilities that always start with a delay rate.

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? 223044

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b) There is no comparison with freely fluctuating currents in the anchor diode yahrsnd the interpulse period »This is a problem with bodies that use either instantaneous © of the average measurements of the positive Voltage cisr anchor diode work »

c) I ¹ ^ e! -! ■ "c / ir.rüfi.oe; G ^ y" / ij:;: Mltni «sss swischisn armature current and Feldstroisi" ard fil ;: jsdea current pulse applied to the motor possible, se that the delays previously required for measuring the average value and the associated measuring arrangements are not required.

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Claims (6)

11 PATENT CLAIMS (1 · j control circuit for controlling a direct current electric motor with an armature, a field and a diode, through it characterized in that the parallel to the armature (A) lying diode (Di) in reverse and thus in I ■ ■ I Reverse direction is pre-polarized) when the motor (A, F) is j is in a driving state that the motor (A, F) i Current pulses are supplied via a direct current switch (S), and that means for checking and determining whether the armature current the field current during each current pulse! i exceeds and means to. Limitation of the current range applied to the motor in the event that the armature current the field current exceeds at a predetermined size, are provided. 2. Control circuit according to claim 1, characterized in that the direct current switch (S) the motor (A, F) supplies current pulses from a direct current source (+ Vb, -Vb) , which in their frequency and / or in their distance ratio in accordance with a Control signal are changeable, that a capacitor (Cl) is present, the charging of which begins with the beginning of each current pulse, and which can be discharged via switching means, which is then in the -12-. 209848/0832 conductive state, when the diode (Di) lies parallel to the armature (A) is reverse biased, whereby during each pulse a check and detection is possible to the effect that the charge on the capacitor (Cl) has reached a predetermined value una the arrangement is such that the motor is supplied with a full strobe range if the predetermined value is not reached and a reduced current range in terms of frequency and / or pulse spacing when the predetermined level has been reached. ■ ". ■ y ,, ■ 3. Control circuit according to Claim 2, characterized in that in the discharge circuit is a transistor (T2), which is the Capacitor (Cl) is connected in parallel, and that the base-emitter circuit of the transistor (T2) at the collector «ittes second transistor (Ti) whose base E »ift« r-KnsJL » is connected in parallel to the armature diode (Dl) 4. Control circuit according to claims 2 and 3, characterized in that that the capacitor (Cl) in series with a charging resistor (R2) and in the output circuit of a transistor (T3) is the basis of which the pulse control or control signals are fed. -13- 209848/0832 5. Control circuit according to claims 2 to 4 ₉ characterized in that means for checking and determining (means for ascertaining) are available for the fact ₃ whether and when the charge of the capacitor has reached a predetermined value, these means being a Zenner "diode (ZDL) which is then transferred to the conducting state when the voltage dropped across the capacitor CCi) voltage reaches the threshold value _s at the susararaenbrichte the voltage dropped across the Zenner diode voltage 6. Control circuit according to claim 5 _P characterized _s that a control signal providing arrangement Cclarap) in a pulse generator, as long as the Zenner diode (ZDL) is in its conductive state is _v actuated _s so that the Frequenzberexch of pulses decreases in the control signal or is reset _o 2098 4 8/0832